1. Field of the Invention
The present invention relates to a magnetostatic wave device, and particularly to a magnetostatic wave device which is used as a filter or the like.
2. Description of the Prior Art
FIG. 7 is an illustrative view showing an example of a conventional magnetostatic wave device. A magnetostatic wave device 2 includes a dielectric substrate 1. As shown in FIG. 8, a ground electrode 3 and strip-line electrodes 4 are formed respectively on both surfaces of the dielectric substrate 2. Micro strip lines as transducers are made with the ground electrode 3 and the strip-line electrodes 4. One end of each of the two strip-line electrodes 4 are connected to the earth electrode 3 via an end face of the dielectric substrate 2. Other ends of the strip-line electrodes 4 are used respectively as an input terminal and an output terminal. A ferrimagnetic base material 5 is arranged on the strip-line electrodes 4. The ferrimagnetic base material 5 is made of a GGG (gadolinium gallium garnet) substrate 6 and a YIG (yttrium iron garnet) thin film 7 formed on the GGG substrate 6. The ferrimagnetic base material 5 is arranged so that the YIG thin film 7 is placed at the side of the strip-line electrodes 4.
When the magnetostatic wave device 1 is used, a magnetic field is supplied to the ferrimagnetic base material 5, and a signal is supplied to the strip-line electrode 4 which is used as an input side. A magnetostatic wave is excited by the input signal, and the magnetostatic wave is propagated on the YIG thin film 7. By receiving the propagated magnetostatic wave, an output signal is obtained from the strip-line electrode 4 which is used as an output side. The magnetostatic wave device 1 has a band-pass characteristics as shown in FIG. 9.
However, the conventional magnetostatic wave device is large, and can not satisfy the needs of miniaturization. Since the magnetostatic wave device is large, the material of the ferrimagnetic base material and the like is used in large quantities, resulting in high manufacturing cost.